Field of the Invention
This invention relates to a process for saponifying tall oil pitch. More particularly, this invention relates to a process for hydrolyzing the fatty acid esters found in a tall oil pitch fraction using small amounts of a cationic amine catalyst at specific conditions.
In the tree, fatty acids are primarily present as triglycerides with some as free fatty acids and a minor percentage as sterol esters. Rosins are present in the tree as free acids mixed with terpenes and other essential oils in a semi-solid mixture known as oleoresin. The majority of the sterols, which function as plant hormones, and the higher fatty alcohols, such as lignoceryl alcohol, are probably present as free alcohols. Hydrolysis of the glycerides to free fatty acids and glycerol occurs by alkaline catalysis in the pulping process.
The fatty acid soaps, rosin acid soaps and unsaponifiables are insoluble in the pulping liquor and are separated therefrom by skimming. The soap skimmings are acidified to form crude tall oil. The crude tall oil contains, among other constituents, its more valuable fatty acids and rosin acids; and it is desirable to recover these materials. The separation of fatty acids from rosin acids is accomplished by distillation. The high temperature and low pressure required for tall oil distillation is conducive to splitting out water between the organic acids and any sterol or long chain fatty alcohol molecules present in the crude tall oil to form esters. These high boiling point esters are the principal components in tall oil pitch, which is the residue from the distillation of crude tall oil. Small quantities of residual lignin and other non-volatile trace materials in tall oil are also present in pitch.
Tall oil pitch, being a residue material, has found uses in areas where color and performance are not critical such as cement additives (U.S. Pat. No. 2,510,776), in asphalt emulsions, certain resins and paper sizes. In any event, attempts have been made to hydrolyze the tall oil pitch esters. If the esters can be hydrolyzed, the acid number is raised making the pitch more valuable and expanding the areas of its use, such as a collector for phosphate in its purification by flotation. However, the tall oil pitch esters are very unreactive and harsh conditions have been found necessary for their saponification. For example, long reflux with aqueous alkali at a temperature above 345.degree.F. (174.degree.C.) and a pressure of about 105 p.s.i.
In view of the foregoing, it should be apparent that there exists a need in the art for improving tall oil pitch. It is, therefore, a primary object of this invention to provide a process for saponifying tall oil pitch. Another object of this invention is to provide a process for hydrolyzing the esters found in tall oil pitch using a cationic amine catalyst.
Still another object of this invention is to provide a process for increasing the acid number of tall oil pitch.
Other objects, features and advantages of this invention will be evident from the following detailed description of the invention.